Erica Synths EDU DIY EG Eurorack Module Kit - Manual (Page 14)

AR VS. ADSR ENVELOPES
And while we could leave it there, I’d rather put in a bit more e ff ort in order to give us finer
control over the envelope curve’s shape. On the left side here, I’ve drawn up what our
current circuit is capable of producing: a simple attack-release-curve. On the other side,
we have a more complex attack-decay-sustain-release curve. What’s the di
ff erence? Well,
while both curves have an attack and a release phase, the one on the right adds a
decay phase and the ability to set a specific sustain level . The idea here is this. If the
sustain is set to a lower value than the envelope’s peak, we get a drop after the attack.
This is the decay phase. Once that’s through, the curve settles on the set sustain level
while the input signal stays high. From here, we enter the release phase once the input
swings low.
What’s the benefit of this added complexity? Simple: we can produce a wider variety of
sounds. Personally, I really like short, plucky, percussive hits – and also gliding acid bass
lines. Both of them are not really doable with a simple attack-release envelope.
Now, turning the circuit we have into a proper ADSR envelope is somewhat out of scope
for this project.
Still, with very little extra e ff ort, we can can build something that
approximates it .
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